The primary goal of the present study is to examine neuropsychiatric changes in exposed patients over time, and to delineate the complex interactions between those changes and particular exposure (e.g., severity), psychosocial (e.g., mood), and biomedical (e.g., vestibular function) variables. A second goal is to identify the specific cognitive processes that are most compromised in individuals who have a history of exposure to organic solvents. To that end, both cross-sectional and longitudinal procedures will be used to evaluate groups of exposed patients, nonexposed controls, and psychiatric controls. All patients who are referred to the University of Pittsburgh Occupational Medicine Clinic who have a history of chronic solvent exposure and complain of neuropsychiatric changes will be given a comprehensive battery of well known neuropsychological and cognitive processing tests, as well as several psychosocial measures. A control group of demographically similar individuals who have no history of exposure will also be examined. Because many of the psychiatric symptoms seen in individuals with solvent exposure resemble the somatiform disorders, a second control group will be composed of psychiatric patients who meet DSM-III criteria for somatization disorder. All subjects will be given a second assessment approximately one year later. The proposed study will attempt to describe and understand how exposed patients differ, both cognitively and emtionally, from normal and psychiatric controls, and how different exposure and biomedical variables affect neuropsychiatric functioning. By having available this information, we will be able to identify both intraindividual and exposure related "risk factors." As a consequence, we will be in a better position to more accurately predict which exposed individuals will actually go on to develop neuropsychiatric symptoms. Results from the longitudinal component of the proposed study will also allow one to make more accurate predictions about long-term prognosis in those individuals with clinically evident neuropsychiatric symptomatology.